Tidal and Residual Circulation in Long Island Sound (Paperback)

A three-dimensional numerical hydrodynamic model for Long Island Sound is applied to examine the spatial structure of the tidal and residual circulation in the basin. Momentum diagnostics are used to analyze the dynamics controlling the longitudinal and lateral circulation. At tidal periods, the longitudinal momentum balance involves local acceleration, barotropic pressure gradient, and stress divergence; the lateral momentum balance involves local acceleration, barotropic pressure gradient, and Coriolis acceleration, with some contribution from the baroclinic pressure gradient at depth. Tidal period lateral circulation is driven primarily by the imbalance between barotropic pressure gradient and Coriolis acceleration. The residual longitudinal momentum balance involves primarily longitudinal advection and the total longitudinal pressure gradient. Results indicated that residual longitudinal advection arises from the interaction of tidal period lateral motion and lateral gradients in longitudinal tidal currents. They indicate further that residual longitudinal advection and longitudinal baroclinic pressure gradient represent driving forces of the same order throughout much of the basin. The residual lateral momentum balance is essentially geostrophic. Results are consistent with recent theoretical models for tidal and residual circulation in elongated rotating basins. Features of the simulated tidal period and residual current structure compare favorably with those features derived from available ADCP current observations in the central Long Island Sound.